1. Field of the Invention
This invention relates generally to footwear such as a shoe, including an athletic shoe, with a shoe sole, including at least one non-orthotic removable insert formed by a midsole portion. The removable midsole portion is inserted into the foot opening of the shoe upper, the sides of which hold it in position, as may the bottom sole or other portion of the midsole. The shoe sole includes a concavely rounded side or underneath portion, which may be formed in part by the removable midsole portion. The removable midsole portion may extend the length of the shoe sole or may form only a part of the shoe sole and can incorporate cushioning or structural compartments or components. The removable midsole portion provides the capability to permit replacement of midsole material which has degraded or has worn out in order to maintain optimal characteristics of the shoe sole. Also, the removable midsole portion allows customization for the individual wearer to provide tailored cushioning or support characteristics.
The invention further relates to a shoe sole which includes at least one non-orthotic removable midsole insert, at least one chamber or compartment containing a fluid, a flow regulator, a pressure sensor to monitor the compartment pressure, and a control system capable of automatically adjusting the pressure in the chamber or compartment(s) in response to the impact of the shoe sole with the ground surface, including embodiments which accomplish this function through the use of a computer such as a microprocessor.
2. Brief Description of the Prior Art Many existing athletic shoes are unnecessarily unsafe. Many existing shoe designs seriously impair or disrupt natural human biomechanics. The resulting unnatural foot and ankle motion caused by such shoe designs leads to abnormally high levels of athletic injuries.
Proof of the unnatural effect of many existing shoe designs has come quite unexpectedly from the discovery that, at the extreme end of its normal range of motion, the unshod bare foot is naturally stable and almost impossible to sprain, while a foot shod with a conventional shoe, athletic or otherwise, is artificially unstable and abnormally prone to ankle sprains. Consequently, most ordinary ankle sprains must be viewed as largely an unnatural phenomena, even though such ankle sprains are fairly common. Compelling evidence demonstrates that the stability of bare feet is entirely different from, and far superior to, the stability of shod feet.
The underlying cause of the nearly universal instability of shoes is a critical but correctable design flaw. That hidden flaw, so deeply ingrained in existing shoe designs, is so extraordinarily fundamental that it has remained unnoticed until now. The flaw is revealed by a novel biomechanical test, one that may be unprecedented in its extreme simplicity. The test simulates a lateral ankle sprain while standing stationary. It is easily duplicated and may be independently verified by anyone in a minute or two without any special equipment or expertise. The simplicity of the test belies its surprisingly convincing results. It demonstrates an obvious difference in stability between a bare foot and a foot shod with an athletic shoe, a difference so unexpectedly noticeable that the test proves beyond doubt that many existing shoes are unstable and thus unsafe.
The broader implications of this discovery are potentially far-reaching. The same fundamental flaw in existing shoes that is glaringly exposed by the new test also appears to be the major cause of chronic overuse injuries, which are unusually common in running, as well as other chronic sport injuries. Existing shoe designs cause the chronic injuries in the same way they cause ankle sprains; that is, by seriously disrupting natural foot and ankle biomechanics.
The applicant has introduced into the art the concept of a theoretically ideal stability plane as a structural basis for shoe sole designs. That concept, as implemented into shoes such as street shoes and athletic shoes, is presented in U.S. Pat. Nos. 4,989,349, issued on Feb. 5, 1991; 5,317,819, issued on Jun. 7, 1994; and 5,544,429, issued on Aug. 13, 1996, as well as in PCT Application No. PCT/US89/03076 filed on Jul. 14, 1989, and many subsequent U.S. and PCT applications.
The purpose of the theoretically ideal stability plane as described in these applications is primarily to provide a neutral shoe design that allows for natural foot and ankle biomechanics without the serious interference from the shoe design that is inherent in many existing shoes.
Accordingly, it is a general object of one or more embodiments of the invention to elaborate upon the application of the principle of the natural basis for the support, stability and cushioning of the bare foot to shoe designs.
It is still another object of one or more embodiments of the invention to provide a shoe having a sole with natural stability which puts the side of the shoe upper under tension in reaction to destabilizing sideways forces on a tilting shoe.
It is still another object of one or more embodiments of the invention to balance the tension force on the side of the shoe upper substantially in equilibrium to neutralize the destabilizing sideways motion by virtue of the tension in the sides of the shoe upper.
It is another object of one or more embodiments of the invention to create a shoe sole with support and cushioning which is provided by shoe sole compartments, filled with a pressure-transmitting medium like liquid, gas, or gel, that are similar in structure to the fat pads of the foot, and which simultaneously provide both firm support and progressive cushioning.
A further object of one or more embodiments of the invention is to elaborate upon the application of the principle of the theoretically ideal stability plane to other shoe structures.
A still further object of one or more embodiments of the invention is to provide a shoe having a sole contour which deviates in a constructive way from the theoretically ideal stability plane.
A still further object of one or more embodiments of the invention is to provide a sole contour having a shape naturally rounded to the shape of a human foot, but having a shoe sole thickness which is increased somewhat beyond the thickness specified by the theoretically ideal stability plane, either through most of the contour of the sole, or at pre-selected portions of the sole.
It is yet another object of one or more embodiments of the invention to provide a naturally rounded shoe sole having a thickness which approximates a theoretically ideal stability plane, but which varies toward either a greater or lesser thickness throughout the sole or at pre-selected portions thereof.
It is another object of one or more embodiments of the present invention to implement one or more of the foregoing objects by employing a non-orthotic removable midsole portion of the shoe.
It is yet another object of one or more embodiments of the present invention to combine one or more of the foregoing objects with the ability to customize the shoe design for a particular wearer's foot.
It is a still further object of one or more embodiments of the present invention to combine one or more of the foregoing objects with the ability to replace one or more portions of the shoe in order to substitute new portions for worn portions or for the purpose of customizing the shoe design for a particular activity.
These and other objects of the invention will become apparent from the summary and detailed description of the invention which follow, taken with the accompanying drawings.